U.S. patent application number 13/166080 was filed with the patent office on 2012-12-27 for housing, mandrel and bearing assembly for downhole drilling motor.
Invention is credited to Carl S. LEBLANC, Randall C. LEBLANC.
Application Number | 20120325561 13/166080 |
Document ID | / |
Family ID | 46147778 |
Filed Date | 2012-12-27 |
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United States Patent
Application |
20120325561 |
Kind Code |
A1 |
LEBLANC; Randall C. ; et
al. |
December 27, 2012 |
Housing, Mandrel and Bearing Assembly for Downhole Drilling
Motor
Abstract
A downhole housing, mandrel and bearing assembly 100 includes a
flex shaft 20 adapted to connect to a downhole motor power output
309 and a tubular mandrel 30 adapted to connect to a drill bit 370.
A lower tubular housing 60 is adapted to contain a lower bearing
assembly 90 and catch sleeve assembly 110. The catch assembly 110
is adapted to retain the mandrel 30 in the lower housing if the
mandrel breaks. An upper tubular housing 70 contains an upper
bearing assembly 80 and is adapted to connect to a housing 302 of
the downhole motor 301. A method of assembling the downhole
housing, mandrel and bearing assembly 100 is disclosed.
Inventors: |
LEBLANC; Randall C.;
(Lafayette, LA) ; LEBLANC; Carl S.; (Lafayette,
LA) |
Family ID: |
46147778 |
Appl. No.: |
13/166080 |
Filed: |
June 22, 2011 |
Current U.S.
Class: |
175/107 ;
175/325.2; 29/428; 384/590 |
Current CPC
Class: |
F16C 19/10 20130101;
Y10T 29/49826 20150115; E21B 4/02 20130101; E21B 10/00 20130101;
E21B 4/003 20130101; E21B 4/00 20130101; F16C 2352/00 20130101;
Y10T 29/49947 20150115; F16C 19/30 20130101 |
Class at
Publication: |
175/107 ;
384/590; 175/325.2; 29/428 |
International
Class: |
E21B 4/00 20060101
E21B004/00; E21B 17/10 20060101 E21B017/10; B21D 39/03 20060101
B21D039/03; F16C 19/30 20060101 F16C019/30 |
Claims
1. A downhole housing, mandrel and bearing assembly comprising: a
flex shaft having: an upper end adapted to receive rotational
torque power from a downhole motor power output, a lower portion
with a longitudinal cavity, at least a portion of said cavity
having threads, a lower end having a connector; a tubular mandrel
adapted at a lower end to connect to a drill bit, said tubular
mandrel having: an upper portion of the mandrel with an external
surface containing threads adapted to connect to the threads in the
longitudinal cavity of the flex shaft, a longitudinal passage
through the mandrel from an upper end to the lower end, a shoulder
disposed on a portion of the external surface of the tubular
mandrel between the upper portion of the mandrel and a lower
portion of the mandrel, said upper portion having a first outside
diameter d1 and said second portion having a second outside
diameter d2, wherein the second outside diameter d2 is greater than
the first outside diameter d1; a lower tubular housing having: a
longitudinal passage from an upper end of the housing to a lower
end of the housing, an upper portion having threads disposed on at
least a portion of an external surface, a shoulder disposed between
the upper portion of the housing and a lower portion of the
housing, said upper portion having a first inside diameter d3 and
said lower portion having a second inside diameter d4, wherein the
second inside diameter d4 is greater than the first inside diameter
d3; an upper tubular housing having: a longitudinal passage from an
upper end of the housing to a lower end of the housing, said
longitudinal passage having a lower portion with an internal
diameter adapted to receive an upper bearing assembly, said lower
portion of the internal passage adapted to connect to the threads
on the upper portion of the lower tubular housing; an upper bearing
assembly disposed in the internal passageway of the upper housing,
said bearing assembly having at least an upper race member, a
middle race member disposed below the upper race member and
separated from the upper race member by a plurality of thrust
balls, and a lower race member disposed below the middle race
member and separated from the middle race member by a plurality of
thrust balls; and a lower bearing assembly disposed in the internal
passageway of the lower housing, said bearing assembly having at
least an upper race member that is adapted to be received in the
shoulder of the lower housing, a middle race member disposed below
the upper race member and separated from the upper race member by a
plurality of thrust balls, and a lower end race member disposed
below the middle race member and separated from the middle race
member by a plurality of thrust balls.
2. The assembly of claim 1 further including: an upper preload
spring assembly disposed in an exterior circumferential recess in
the lower portion of the flex shaft, said spring assembly
comprising: a first resilient member with a first end contacting a
ledge in recess and a second end contacting a first end of a spacer
member; and a second resilient member with a first end contacting a
second end of the spacer member and a second end contacting the
upper end of the upper bearing assembly.
3. The assembly of claim 1 further including: a lower preload
spring assembly disposed in an exterior circumferential recess in a
catch assembly, said spring assembly comprising: a first resilient
member with a first end contacting a ledge in recess and a second
end contacting a first end of a spacer member; and a second
resilient member with a first end contacting a second end of the
spacer member and a second end contacting the lower end of the
lower bearing assembly.
4. The assembly of claim 1 further including: a tubular catch
sleeve disposed on a lower portion of the tubular mandrel, said
catch sleeve having: an internal passageway adapted to contact the
shoulder of the tubular mandrel; an exterior surface adapted to be
received in the longitudinal passageway of the lower housing; an
upper end having a connector adapted to connect to the bearing; a
portion of the internal passageway having at least two flats
adapted to mate to at least two flats on a portion of the tubular
mandrel.
5. The assembly of claim 4 wherein there are eight flats in the
internal passageway forming a female hex connector and there are
eight flats on a portion of the mandrel that form a male hex
connector.
6. The assembly of claim 4 further including: at least two radial
receptacles disposed in the lower portion of the tubular mandrel,
each of said receptacles adapted to receive a locking pin adapted
to secure the catch sleeve to the tubular mandrel.
7. The assembly of claim 4 further including: a radial sleeve
disposed in the lower end of the lower housing, said radial sleeve
adapted to retain the catch sleeve inside the lower housing.
8. The upper bearing assembly of claim 1 wherein the upper race
member has an upper end having a connector adapted to connect to
the flex shaft thereby securing the upper race to the flex shaft
such that the upper race member rotates with the flex shaft and
with the mandrel as the flex shaft and mandrel are rotated in
drilling operations.
9. The upper bearing assembly of claim 1 wherein the middle race
section is free to rotate with and about the mandrel during
drilling operations.
10. The upper bearing assembly of claim 1 wherein the lower race
member has a lower end that includes a connector that secures the
lower race member to a connector at an upper end of the lower
tubular housing.
11. The lower bearing assembly of claim 4 wherein the lower race
member has a lower end that includes a connector that secures the
lower race member to a connector at the upper end of the catch
assembly, thereby securing the lower race member to the catch
assembly, and wherein the catch assembly is secured to the
mandrel.
12. The assembly of claim 1 wherein each bearing member is a single
unitary piece.
13. A catch sleeve assembly for a downhole bearing and mandrel
assembly, said catch sleeve assembly comprising: a tubular mandrel
adapted at a lower end to connect to a drill bit, a shoulder
disposed on a portion of the external surface of the tubular
mandrel between the upper portion of the mandrel and a lower
portion of the mandrel, said upper portion having a first outside
diameter d1 and said second portion having a second outside
diameter d2, wherein the second outside diameter d2 is greater than
the first outside diameter d1, said mandrel further including a
longitudinal passage through the mandrel from an upper end to the
lower end; a tubular housing having a longitudinal passage from an
upper end of the tubular housing to a lower end of the housing; a
tubular catch sleeve having an exterior surface adapted to be
received in the longitudinal passageway of the tubular housing,
said catch sleeve further having an internal passageway adapted to
contact the shoulder of the tubular mandrel when the tubular catch
sleeve is disposed on the tubular mandrel, and wherein a portion of
the internal passageway has at least two flats adapted to mate to
at least two flats on a portion of the tubular mandrel; and a
radial sleeve disposed in the lower end of the lower housing, said
radial sleeve adapted to retain the catch sleeve inside the lower
housing.
14. A downhole bearing and housing assembly comprising: a lower
tubular housing having: a longitudinal passage from an upper end of
the housing to a lower end of the housing, an upper portion having
threads disposed on at least a portion of an external surface, a
shoulder disposed between the upper portion of the housing and a
lower portion of the housing, said upper portions having a first
inside diameter d3 and said lower portion having a second inside
diameter d4, wherein the second inside diameter d4 is greater than
the first inside diameter d3; an upper tubular housing having: a
longitudinal passage from an upper end of the housing to a lower
end of the housing, said longitudinal passage having a lower
portion with an internal diameter adapted to receive an upper
bearing assembly, said lower portion of the internal passage having
threads disposed on at least a portion of an internal surface of
the internal passageway, said threads adapted to connect to the
threads of the upper portion of the lower tubular housing; an upper
bearing assembly disposed in the internal passageway of the upper
housing, said bearing assembly having an upper race member, a
middle race member disposed below the upper race member and
separated from the upper race member by a plurality of thrust
balls, and a lower race member disposed below the middle race
member and separated from the middle race member by a plurality of
thrust balls; and a lower bearing assembly disposed in the internal
passageway of the lower housing, said bearing assembly having an
upper race member that is adapted to be received in the shoulder of
the lower housing, a middle race member disposed below the upper
race member and separated from the upper race member by a plurality
of thrust balls, and a lower end race member disposed below the
middle race member and separated from the middle race member by a
plurality of thrust balls.
15. The upper bearing assembly of claim 14 wherein the upper race
member has an upper end having a connector adapted to connect to
the flex shaft, thereby securing the upper race to the flex shaft
such that the upper race member rotates with the flex shaft and
with the mandrel as the flex shaft and mandrel are rotated in
drilling operations.
16. The upper bearing assembly of claim 14 wherein the middle race
section is free to rotate with and about the mandrel during
drilling operations.
17. The upper bearing assembly of claim 14 wherein the lower race
member has a lower end that includes a connector that secures the
lower race member to a connector at an upper end of the lower
tubular housing.
18. The lower bearing assembly of claim 14 wherein the lower race
member has a lower end that includes a connector that secures the
lower race member to a connector at the upper end of the catch
assembly, thereby securing the lower race member to the catch
assembly, and wherein the catch assembly is secured to the
mandrel.
19. The assembly of claim 14 wherein each bearing member is a
single unitary piece.
20. A method of assembling a downhole drilling assembly comprising
the steps of: providing a tubular mandrel having a bit box at a
lower end adapted to connect to a drill bit, said mandrel having an
upper portion of the mandrel having an external surface containing
threads adapted to connect to the threads of the lower portion of
the flex shaft, a shoulder disposed on a portion of the external
surface of the tubular mandrel between the upper portion of the
mandrel and a lower portion of the mandrel, sliding a retaining
ring downwardly from an upper end of the mandrel until it rests on
an outer radius of the bit box at the lower end of the mandrel;
sliding a radial sleeve over the mandrel from the top until it
rests on the retaining ring; sliding a tubular catch sleeve over
the top of the mandrel until a lower female hex connector disposed
in a longitudinal passageway through the catch sleeve is positioned
over a male hex connector of the mandrel and an interior surface of
the passageway of the catch sleeve abuts the shoulder of the
mandrel; inserting locking pins into receptacles in the mandrel to
secure the catch sleeve to the mandrel; sliding a lower bearing
assembly over the mandrel and positioning the bearing assembly on a
top of the catch sleeve; sliding a lower tubular housing over the
mandrel and positioning the lower housing such that a ledge of the
lower housing contacts the upper end of the lower bearing assembly;
inserting a retaining ring into the lower end of the lower housing;
sliding an upper bearing assembly over the mandrel and positioning
the bearing assembly with a lower female hex connector of the
bearing assembly onto an upper male hex connector of the lower
housing; positioning a tubular flex shaft over the upper end of the
mandrel and threadedly connecting the flex shaft to the upper end
of the mandrel; and positioning an upper tubular housing over the
flex shaft and threadedly connecting the upper tubular housing to
the lower tubular housing.
21. The method of claim 20 further including the steps of:
connecting a power output of a downhole motor to the upper end of
the flex shaft; and positioning the stator and motor housing of the
downhole motor over the upper end of the flex shaft.
22. The method of claim 21 further including connecting an upper
end of the motor housing to a cross-over sub that is connected to a
drill string.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to improvements in
downhole drilling equipment and more particularly pertains to a new
improved housing, mandrel and bearing assembly for transmitting
power from a downhole drilling motor output to a drill bit.
BACKGROUND
[0002] Downhole drilling motors have been used for many years in
the drilling of oil and gas wells and other wells. In the usual
mode of operation, the rotational power output shaft of the motor
and the drill bit will rotate with respect to the housing of the
motor. The housing, in turn, is connected to a conventional drill
string composed of drill collars and sections of drill pipe. This
drill string extends to the surface. Drilling fluid is pumped down
through the drill string to the bottom of the hole and back up the
annulus between the drill string and the wall of the bore hole. The
drilling fluid cools the drill bit and removes the cuttings
resulting from the drilling operation. In the instances where the
downhole drilling motor is a hydraulic powered type, such as a
positive displacement type motor, the drilling fluid also supplies
the hydraulic power to operate the motor. See FIG. 1.
[0003] Virtually all downhole drilling motors have three basic
components:
[0004] 1. Motor section
[0005] 2. Vertical thrust bearings
[0006] 3. Radial bearings
[0007] The bearings can be placed in a separate package or unit at
the motor section and thus can be used on any type of motor (i.e.,
turbodrills, positive displacement motors, etc.).
[0008] There are two basic types of downhole drilling motors:
[0009] 1. Turbodrills
[0010] 2. Positive displacement motors.
[0011] Turbodrills utilize the momentum change of drilling fluid
(i.e., mud) passing through curved turbine blades to provide power
to turn the bit. Turbodrills turn at speeds of 600 to 3,000 rpm.
Positive displacement motors have fixed volumetric displacement and
their speed is directly proportional to the flow rate of the
hydraulic power fluid. There are two basic types of positive
displacement motors in use:
[0012] 1. Moineau motors have a helical rotor within the cavity of
a stator which is connected to the housing of the motor. As the
drilling fluid is pumped down through the motor, the fluid rotates
the rotor.
[0013] 2. Vane motors have large volumetric displacement and
therefore deliver higher torques at lower speeds.
[0014] Thrust bearing failure in downhole motors is a problem
because of high dynamic loads produced by the action of the bits
and by drill string vibrations. One major oil company placed a
recorder at the hole bottom and found that dynamic loads were often
50% higher than the applied bit weight. It was found on occasion
that the bit bounced off bottom and produced loads in excess of
120,000 pounds when drilling at an applied bit weight of 40,000
pounds. See discussion in U.S. Pat. No. 4,246,976, incorporated by
reference. These high loads can cause rapid failure of the thrust
bearings and bearing mandrels; consequently, these bearings must be
greatly over-designed to operate in the hostile downhole
environment.
[0015] At least two types of thrust bearings have been used in
downhole drilling motors:
[0016] 1. Rubber friction bearings
[0017] 2. Ball or roller bearings.
[0018] Radial bearings are required between the bearing housing and
the rotating mandrel transmitting power from the motor power output
to the bit. Radial bearings are usually subjected to lower loads
than the thrust bearings and therefore have much longer life. The
basic types of radial bearings used in downhole motors are:
[0019] 1. Marine bearings
[0020] 2. Roller or ball bearings
[0021] 3. Metal to metal carbide bearings.
[0022] Most motors contain metal to metal radial bearings. These
bearings are frequently lubricated by circulating mud through them.
However, some bearing systems are sealed and are lubricated using
lubricant (grease) injected into the bearing by a hydraulic piston
assembly.
[0023] For a further discussion of downhole drilling motors and
their operations, see U.S. Pat. Nos. 3,840,080; 4,246,976;
4,492,276; 5,495,900; 5,090,497; 6,183,226; 6,905,319 and Canadian
Patent No. 2,058,080, incorporated by reference.
SUMMARY
[0024] The present disclosure pertains to a new improved housing,
mandrel and bearing assembly for transmitting power from a downhole
drilling motor output to the drill bit. Rotational
power=torque.times.RPM/5250. The invention provides a reduced
length housing, bearing and mandrel assembly used in downhole
drilling operations. Reduced length provides the following
advantages: [0025] 1. Ability to more effectively navigate around
deviated sections of the wellbore by reducing friction caused as a
section of the bottom hole assembly goes in and out of these
deviated sections which ultimately causes premature wear on
internal components. [0026] 2. A reduced bit to bend allows the
drill motor to build greater angle with less of an incorporated fix
bend to get to desired lateral. This reduced degree bent housing
ultimately reduces wear and tear on internal components.
[0027] As used in this document, "tubular" refers to a generally
cylindrical member with a longitudinal passage therethrough. The
longitudinal passage may be formed therein or bored
therethrough.
[0028] A downhole housing, mandrel and bearing assembly 100 is
disclosed herein. The assembly includes a flex shaft 20 having an
upper end 21 with a threaded male pin adapted to connect to a
helical rotor power output 309 and a lower end 25 having a male hex
connector 26. The assembly further includes a tubular mandrel 30
adapted at a lower end 31 to connect to a drill bit, said mandrel
having an upper portion 33 of the mandrel 30 adapted to connect to
the lower portion 27 of the flex shaft 20 and a longitudinal
passage 32 through the mandrel from an upper end 35 to the lower
end 31. The assembly further includes a lower tubular housing 60
having a longitudinal passage 66 from an upper end 61 of the
housing to a lower end 63 of the housing wherein the upper end 61
further has a male hex connector 62. The assembly includes an upper
tubular housing 70 having a longitudinal passage 76 from an upper
end 71 of the housing to a lower end 73 of the housing wherein the
passage has a lower portion 74 with an internal diameter adapted to
receive the upper bearing assembly 80 and the lower portion 74 of
the internal passage is adapted to connect to the male upper
portion of the lower tubular housing 60. An upper bearing assembly
80 is disposed in the internal passageway 76 of the upper housing
70. The bearing assembly includes an upper bearing race member 82
having an upper female hex box connector 83 adapted to receive the
male hex connector 26 of the flex shaft 20. A center bearing race
86 is disposed below the upper race member 82 and separated by a
plurality of thrust balls 85. A lower bearing race member 87 is
disposed below the center bearing, the lower race member has a
lower end that includes a lower female hex box connector 89 that
secures the lower race member to the male hex connector 62 at the
upper end 61 of the lower tubular housing 60. A plurality of thrust
balls 85 are disposed between the middle race member 86 and the
lower race member 87. A lower bearing assembly 90 is disposed in
the internal passageway 66 of the lower housing 60, wherein the
bearing assembly includes a generally cylindrical body with an
upper end 92 adapted to be received in shoulder 67 of the lower
housing 60. A middle bearing race member 96 is disposed below the
upper bearing race member 92 and separated by a plurality of thrust
balls 95. A lower bearing race member 93 is disposed below the
middle race member 96. The lower race member has a lower end that
includes a lower female hex box connector 94 that secures the lower
race member to a male hex connector 116 at the upper end of the
catch assembly 110. A plurality of thrust balls 85 are disposed
between the middle race member 96 and the lower race member 93. The
assembly further includes a catch sleeve 110 disposed on a lower
portion of the tubular mandrel 30. The catch sleeve includes an
internal passageway 112 adapted to contact the tubular mandrel
wherein an exterior surface of the catch sleeve is adapted to be
received in longitudinal passageway 66 of lower housing 60. An
upper end 115 of the catch sleeve has an upper male hex connector
116 adapted to receive the female hex connector 94 of the lower
bearing member 93. A lower portion of the internal passageway 112
of the catch sleeve has a hexagonal cross-section adapted to
receive a hexagonal cross-section of a portion 36 of the tubular
mandrel. A portion of the internal passageway is adapted to contact
the shoulder 37 of the tubular mandrel. The assembly further
includes at least two radial receptacles 39 disposed in the lower
portion 36 of the tubular mandrel 30, each of the receptacles
adapted to receive a locking pin 41 and secure the catch sleeve to
the tubular mandrel 30. A snap ring holds the locking pin 41 in
place. The assembly further includes a radial sleeve 120 disposed
in the lower end 63 of the lower housing 60, locked within the
lower housing by radial dowel pins 124 that secures the radial
sleeve to the lower housing and in operation the mandrel rotates in
the radial sleeve and the lower housing. The radial sleeve is held
within the housing with the retaining ring 122. This retaining ring
122 serves to hold the radial sleeve within the housing and extract
the lower mandrel in the event of a fracture within the upper
section of the mandrel.
[0029] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
DESCRIPTION OF DRAWINGS
[0030] FIG. 1 is a schematic illustrating a typical drilling system
using a downhole drilling motor assembly;
[0031] FIG. 2 is a cross-section of a prior art bearing and bearing
mandrel assembly of a prior art downhole motor;
[0032] FIG. 2A is a cross-section of the bearing mandrel of the
prior art assembly of FIG. 2;
[0033] FIG. 3 is a cross-section of a housing, mandrel and bearing
assembly of the present disclosure;
[0034] FIG. 4 is an enlarged cross-section of an upper portion of
the assembly of FIG. 3;
[0035] FIG. 4A is a cross-section illustrating a portion of a flex
shaft of the assembly of FIG. 4;
[0036] FIG. 4B is a lateral cross-section of the flex shaft of FIG.
4A taken at section AA;
[0037] FIG. 4C is a cross-section of a bearing assembly member of
FIG. 4;
[0038] FIG. 4D is a lateral cross-section of an upper end of the
bearing assembly member of FIG. 4 taken at Section AA;
[0039] FIG. 4E is a cross-section of the upper end of the lower
housing of FIG. 4;
[0040] FIG. 4F is a lateral cross-section of the upper end of the
lower housing of FIG. 4 taken at section BB;
[0041] FIG. 5 is a cross-section of a lower portion of the assembly
of FIG. 3;
[0042] FIG. 5A is a cross-section illustrating a portion of a
tubular mandrel and a catch assembly of FIG. 5;
[0043] FIG. 5B is a lateral cross-section of the tubular mandrel
and the catch assembly of
[0044] FIG. 5A taken at section CC of FIG. 5;
[0045] FIG. 5C is a cross-section of a lower bearing assembly of
FIG. 5;
[0046] FIG. 5D is a lateral cross-section of the lower bearing
assembly of FIG. 5 taken at section DD;
[0047] FIG. 6 is a cross-section illustrating the flow of drilling
fluid down the drill string, through a downhole drilling motor,
through the assembly of FIG. 3, out a bit and up the annulus of the
wellbore;
[0048] FIGS. 7A and 7B are a cross-section illustrating the
transfer of downward force and upward force from a drill string
through the assembly of FIG. 3 to a drill bit;
[0049] FIGS. 8A to 8K are partial cross-sections illustrating the
sequential steps of assembling the housing, mandrel and bearing
assembly of FIG. 3; and
[0050] FIGS. 9A and 9B are a cross-section illustrating the
assembly of FIG. 3 before failure of the mandrel and after failure
of the mandrel wherein the catch sleeve and radial sleeve maintain
the broken mandrel in the assembly.
[0051] FIG. 10 is a cross-section of a prior art bearing used in a
downhole motor.
[0052] FIG. 11 is a cross-section of the upper housing and the
upper and the lower bearing assemblies of the assembly of FIG.
3.
[0053] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0054] FIG. 1 illustrates a simplified schematic of a drilling
operation. A drill string 310 extends to the surface 348 where it
is connected to a kelly 320, mounted in a rotary table 330 of a
drilling rig 340 to provide rotation to the drill string 310 when a
downhole motor is not used to provide rotation to the bit.
Alternatively, top drive systems are suspended in a rig derrick 342
and provide rotation directly to the drill string 310. Drilling
fluid 350 is pumped down through the drill string 310 to the bottom
of the bore hole 360 and back up the annulus 362 between the drill
string 310 and the wall of the bore hole 360. The drilling fluid
cools the drill bit 370 and removes the cuttings resulting from the
drilling operation.
[0055] In certain drilling situations, including but not limited to
directional drilling, it is useful to use a downhole drilling motor
assembly 301 to provide rotation to the bit. In such situations the
downhole motor assembly 301 is inserted into the drill string 310
above the drill bit 370. In the instances where the downhole
drilling motor is a hydraulic type, such as a progressive cavity
type motor, the drilling fluid 350 also supplies the hydraulic
power to operate the motor.
[0056] Various types of downhole drilling motors may be employed
for the purpose of the invention such as electrical motors and
hydraulic motors. Suitable hydraulic motors are turbines, vane
motors and Moineau motors. See discussion in background section of
this document about various types of drilling motors.
[0057] A Moineau motor is very useful for application in the
present invention since this type of motor is provided with a
flexible connection between the rotor and power output shaft to
compensate the eccentric movement of the rotor in the housing
during operation of the motor. The invention is not restricted to
the use of a Moineau motor. Any type of downhole motor known in the
art may be used with the bearing mandrel and bearing assembly of
the present invention.
[0058] FIG. 2 illustrates a partial cross-section of a prior art
downhole motor bearing assembly and bearing mandrel assembly. A
downhole drilling motor (not shown) transmits power from the motor
power output 491 to a bearing mandrel 490 that contacts radial
bearings 493 and thrust bearings 492 housed in a bearing housing
494. The mandrel's distal (lower) end 497 includes a bit box 498
connection for connection to a drill bit. The box connection
results in assembly configurations that do not allow the mandrel to
be assembled by insertion of the mandrel through the proximal
(upper end) 499 of the bearing housing 494. These prior art
configurations have mandrels with stepped down profiles 496 on
which a bearing spacer 495 makes contact. FIG. 2A illustrates one
embodiment of a cross-section of the prior art bearing mandrel
490.
[0059] As weight is applied on the bit, a downward force DF will
move down the drill string through the motor and to the mandrel
490. As the mandrel 490 moves downward, bearing spacer 491 will
push thrust bearings 492 down. Bearing spacer 495 will contact
mandrel 490 at the step down 496. When it does, it will provide
weight to the bit to start drilling. An equal and opposite upward
force UF will be exerted by the bottom of the bore hole below the
bit.
[0060] FIG. 3 illustrates a partial cross-section of a downhole
motor assembly 301 that includes a tubular housing 302 that is
preferably formed of steel. Disposed within the tubular housing 302
is a power unit having a stator 306 and a rotor 308 connected to a
power output assembly 309. The power output assembly 309 may be
attached directly to the housing, mandrel and bearing assembly 100
according to one embodiment of the present invention or may include
intermediate assemblies that ultimately connect to the housing,
mandrel and bearing assembly 100 of the present invention.
[0061] Referring to both FIGS. 1 and 6, in operation, drilling
fluid 350 (also known in the art as drilling mud) is pumped down
the interior of a drill string attached to downhole drilling motor
301. Drilling fluid 350 enters the drilling motor 301 having a
pressure that is a combination of pressure imposed on the drilling
fluid by pumps at the surface and the hydrostatic pressure of the
above column of drilling fluid 350. The pressurized fluid entering
a cavity in the motor, in cooperation with the lobes of the stator
306 and the geometry of the stator 306 and rotor 308 causes the
lobes of the stator to deform and the rotor to turn to allow the
drilling fluid 350 to pass through the motor 301. Drilling fluid
350 subsequently exits through ports (referred to in the art as
jets) in drill bit 370 and travels up the annulus 362 between the
bit 370, the assembly 100 of the present invention and the downhole
motor assembly 301 and drill string 310 and is received at the
surface 348 where it is captured and pumped down the drill string
310 again.
[0062] Referring to FIGS. 3 through 5D, therein is illustrated one
embodiment of a downhole housing, mandrel and bearing assembly 100
of the present invention. The assembly has a flex shaft 20 with an
upper end 21 adapted to connect to a downhole motor power output
309. The flex shaft has a lower portion 27 with a longitudinal
cavity 23, at least a portion of said cavity having female threads
24 and a lower end 25 having a male hex connector 26. It will be
understood that other forms of connectors such as spline
connectors, pins and threaded connectors may be used.
[0063] The assembly further includes a tubular mandrel 30 adapted
at a lower end 31 to connect to a drill bit. The outer surface of
the mandrel is generally cylindrical (except as noted herein) with
an outer diameter that is smaller than the inner diameter of an
upper housing 70 and a lower housing 60, allowing the mandrel to
rotate in the housings. The mandrel has an upper portion 33 with an
outer surface containing male threads 34 adapted to connect to the
female threads 24 of the lower portion 27 of the flex shaft 20. The
mandrel includes a longitudinal passage 32 through the mandrel from
an upper end 35 to the lower end 31. A shoulder 37 is disposed
between the upper portion 33 having a first outside diameter d1 and
a lower portion 36 having a second outside diameter d2, wherein the
second outside diameter d2 is greater than the first outside
diameter d1. A series of flats (see FIGS. 5 and 5B) are disposed on
the outer surface in the lower portion 36 of the mandrel 30 to form
a male hex connector 38 upon which a catch assembly 110 is
positioned. It will be understood that the series of flats may be
six as in a hex connector or may be 2 or more flats that are sized
and configured to mate with an interior surface of the catch
assembly 110 and connect the mandrel to the catch assembly such
that the catch assembly rotates with the mandrel during drilling
operations, and does not rotate about the mandrel. It will be
understood that other forms of connectors such as spline
connectors, pins and threaded connectors may be used.
[0064] The assembly further includes a lower tubular housing 60
having a longitudinal passage 66 from an upper end 61 of the
housing to a lower end 63 of the housing. The lower tubular housing
includes an upper portion 65 having male threads 68 disposed on at
least a portion of an external surface. A shoulder 67 is disposed
between the upper portion 65 having a first inside diameter d3 and
a lower portion 69 having a second inside diameter d4 wherein the
second outside diameter d4 is greater than the first outside
diameter d3. The upper end 61 further includes a male hex connector
62. It will be understood that the male connector may include a
series of 6 flats as in a hex connection or may include two or more
flats wherein the flats are configured to mate with a female
connector of a bearing race member 87 to be joined to the male
connector 62. It will be understood that other forms of connectors
such as spline connectors, pins, and threaded connectors may be
used.
[0065] The assembly further includes an upper tubular housing 70
having: a longitudinal passage 76 from an upper end 71 of the
housing to a lower end 73 of the housing. The passage has a lower
portion 74 with an internal diameter adapted to receive an upper
bearing assembly 80. The lower portion 74 of the internal passage
76 has female threads 75 disposed on at least a portion of an
internal surface of the internal passageway, said threads adapted
to connect to the male threads 68 of the upper portion of the lower
tubular housing 60. The upper housing further includes an upper
portion 77 adapted to connect to a stator 302 of a downhole
drilling motor 301.
[0066] The assembly 100 further includes an upper bearing assembly
80 (see FIGS. 4 and 5) disposed in the internal passageway 76 of
the upper housing 70, wherein the upper bearing assembly has at
least three bearing race members each having a generally
cylindrical body. An upper end race member 82 has an upper end
having an upper female hex box connector 83 (see FIGS. 4C and 4D)
adapted to receive the male hex connector 26 of the flex shaft 20
(see FIGS. 4A and 4B). The hex connector secures the upper race 82
to the flex shaft such that the upper race rotates with the flex
shaft and with the mandrel 30 as the flex shaft and mandrel are
rotated in drilling operations. It will be understood that other
forms of connectors such as spline connectors, pins and threaded
connectors may be used. A middle race member 86 is disposed below
the upper race member 82 and separated by a plurality of thrust
balls 85. The middle race section 86 is free to rotate with and
about the mandrel during drilling operations. A lower end race
member 87 is disposed below the middle race member 86. The lower
race member has a lower end that includes a lower female hex box
connector 89 that secures the lower race member to the male hex
connector 62 at the upper end 61 of the lower tubular housing 60
(see FIGS. 4E and 4F). It will be understood that other forms of
connectors such as spline connectors, pins and threaded connectors
may be used. Therefore, the lower end race member 87 is fixed to
the lower housing 60 and does not rotate with the mandrel 30. A
plurality of thrust balls 85 are disposed between the middle race
member 86 and the lower race member 87.
[0067] The assembly further includes a lower bearing assembly 90
disposed in the internal passageway 66 of the lower housing 60,
wherein the bearing assembly has an upper race member 92 that is
adapted to be received in shoulder 67 of lower housing 60. Upper
race member 92 may rotate with and about the mandrel during
rotation of the mandrel during drilling operations. A middle race
member 96 is disposed below the upper end race member 92 and
separated by a plurality of thrust balls 95 (see FIGS. 5D and 5C).
The middle race section 96 is free to rotate with and about the
mandrel during drilling operations. A lower end race member 93 is
disposed below the middle race member 96. The lower race member has
a lower end that includes a lower female hex box connector 94 that
secures the lower race member to a male hex connector 116 at the
upper end of a catch assembly 110 (see FIGS. 5A and 5B). It will be
understood that other forms of connectors such as spline
connectors, pins and threaded connectors may be used. Therefore,
the lower race member 93 is fixed to the catch assembly 110 and
rotates with the mandrel 30. The catch assembly 110 is secured to
the mandrel as described later herein. Therefore, the race member
93 rotates with the mandrel. A plurality of thrust balls 85 are
disposed between the middle race member 96 and the lower race
member 93 (see FIGS. 5C and 5D).
[0068] The assembly further includes an upper preload spring
assembly 130 disposed in an exterior circumferential recess 29 in
the lower portion 27 of the flex shaft 20. The spring assembly has
a first resilient member 131 with a first end contacting a ledge 28
in recess 29 and a second end contacting a first end of a spacer
member 132; and a second resilient member 133 with a first end
contacting a second end of spacer member 132 and a second end
contacting the upper end of the upper bearing assembly member
82.
[0069] The assembly further includes a lower preload spring
assembly 140 disposed in an exterior circumferential recess 119 in
catch sleeve 110. The spring assembly has a first resilient member
141 with a first end contacting a ledge 113 in recess 119 and a
second end contacting a first end of a spacer member 142; and a
second resilient member 143 with a first end contacting a second
end of spacer member 142 and a second end contacting the lower end
97 of the lower bearing assembly 90.
[0070] The assembly further includes a radial sleeve 120 disposed
in the lower end 63 of the lower housing 60. The radial sleeve 120
is locked within the lower housing by vertical dowel pin 124 that
maintains the radial sleeve rotating with the lower housing around
the mandrel during motor operation. The radial sleeve is held
within the housing 60 with the retaining ring 122. This retaining
ring 122 serves to hold the radial sleeve within housing 60 and
extract the lower mandrel 30 and catch sleeve 110 in the event of a
fracture within the upper section of the mandrel (see FIGS. 9A and
9B.
[0071] The assembly further includes a catch sleeve 110 having an
internal passageway 112 adapted to contact the shoulder 37 of the
tubular mandrel. The catch sleeve further includes an exterior
surface adapted to be received in longitudinal passageway 66 of
lower housing 60, and an upper end 115 having an upper male hex
connector 116 adapted to receive the female hex connector 94 of the
bearing 90. As illustrated in FIGS. 5, 5A and 5B, the tubular
mandrel 30 has a portion of the exterior surface wherein the outer
perimeter is configured as a hexagon in the portion of the mandrel
on which the catch sleeve 110 is disposed. The catch sleeve
passageway has an internal surface wherein the perimeter is
configured as a hexagon adapted to mate with the outer surface of
the tubular mandrel. It will be understood that other forms of
connectors such as spline connectors, pins and threaded connectors
may be used. When the catch sleeve 110 is in position the catch
sleeve will move with the rotating mandrel during drilling
operations, not about the mandrel. The assembly 100 further
includes at least two radial receptacles 39 disposed in the lower
portion 36 of the tubular mandrel, each of said receptacles is
adapted to receive a locking pin 41. The pins secure the catch
assembly to the mandrel.
[0072] The unique design of the assembly 100 provides many
advantages over the prior art designs. For example, if the mandrel
30 were to break above the catch sleeve the mandrel can be removed
from the wellbore 360 together with the upper 70 and lower 60
housings using the drill string 310. This configuration is
desirable as it prevents the undesirable situation of leaving a
portion of broken mandrel 30 and drill bit 370 in the wellbore,
which must be retrieved in a difficult operation often referred to
in the art as "fishing." Due to the unique configuration of the
assembly of the present invention the broken mandrel 30 and drill
bit 370 would be pulled from the wellbore using the drill string.
Because of the configuration of the catch sleeve 110, the mandrel
30 and lower housing 60, the mandrel will not fall out of the lower
housing 60 and be left in the wellbore 360.
[0073] Referring now to FIG. 7A,wherein there is illustrated the
transfer of downward force DF through the assembly 100 to the bit
370 during drilling operations. Downward force DF is transmitted
through the upper housing 70 and lower housing 60 through the lower
bearing 90 and catch sleeve 110 to the shoulder 37 of the mandrel
30 and through the mandrel to the bit 370. When pulling the drill
string 310 from the hole, removal force RF is transferred through
the upper bearing 80 to the flex shaft 20 which is connected to the
mandrel 30 and through the mandrel 30 to the bit 370 (see FIG.
7B).
[0074] FIGS. 8A to 8K are partial cross-sections illustrating the
sequential steps of assembling the housing, mandrel and bearing
assembly of FIG. 3. In step 1, the mandrel 30, as illustrated in
FIGS. 3, 4 and 5, and described above, is provided. A retaining
ring 122 is slid downward from the top of the mandrel 30 until it
rests on an outer radius of the bit box (See FIG. 8A).
[0075] In step 2, a radial sleeve 120 is slid over the mandrel from
the top until it rests on the retaining ring (see FIG. 8A).
[0076] In step 3 (see FIG. 8B), a catch sleeve 110 is slid over the
top of the mandrel until the lower female hex connector is
positioned over the male hex connector of the mandrel and the catch
sleeve abuts the shoulder 37 of the mandrel.
[0077] In step 4 (see FIG. 8B), locking pins 41 are inserted into
receptacles 39 in mandrel 30 to secure the catch sleeve to the
mandrel.
[0078] In step 5 (see FIG. 8C), one or more lower preload spring
assemblies 140 are inserted onto the catch sleeve and positioned in
recess 119 of the catch assembly 110.
[0079] In step 6 (see FIG. 8D), lower bearing assembly 90 is slid
over the mandrel and positioned on the top of catch sleeve 110.
[0080] In step 7 (see FIG. 8E), lower housing 60 is slid over the
mandrel and positioned such that a ledge contacts the upper end of
the lower bearing assembly. Retaining ring 122 is inserted into the
lower end of the lower housing. The retaining ring 122 keeps the
radial sleeve 120 from falling out the lower end of the housing
60.
[0081] In step 8 (see FIG. 8F), upper bearing assembly 80 is slid
over the mandrel and positioned with the lower female hex connector
of the bearing assembly onto the upper male hex connector of the
lower housing.
[0082] In step 9 (see FIG. 8G), preload spring assembly 130 is slid
over the mandrel and positioned adjacent the bearing assembly 80 to
bias the bearing assembly members together and in contact with the
housing 60.
[0083] In step 10 (see FIG. 8G), flex shaft 20 is positioned over
the upper end of the mandrel and threadedly connected to the upper
end of the mandrel.
[0084] In step 11 (see FIG. 8H), upper housing 70 is positioned
over the flex shaft 20 and threadedly connected to lower housing
60.
[0085] In step 12 (see FIG. 8I), the power output 309 and rotor 308
of downhole motor 301 is connected to the flex shaft 20.
[0086] In step 13 (see FIG. 8J), the stator 306 and motor housing
302 is positioned over the rotor and upper end of the flex
shaft.
[0087] In step 14 (see FIG. 8K), the upper end of motor housing 302
is connected to a cross-over sub that is connected to drill string
310.
[0088] Referring to FIG. 10, wherein is illustrated a cross-section
of a prior art bearing system 580 inside housing 560. The bearing
races are formed from an inside member 582 and an outside member
584. This assembly requires more machining and assembly time than
the bearing assemblies 80 and 90 of the present invention (see FIG.
11). Bearing assemblies 80 and 90 are separated by housing 60.
[0089] Bearing races 82, 86, 87, 92, 96, 93 are a single
construction saving time and money in manufacturing an assembly
when compared to prior art assembly 560.
[0090] It will be understood that threaded and hex connectors have
been disclosed and described in the drawings and specifications;
the present invention may use various types of connectors.
[0091] A number of embodiments of the invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention.
* * * * *